GLOSSARY 391 



Nautilus (naiv' ti lus). An animal belonging to the Cephalopoda, living in a coiled 

 shell divided into chambers. 



Neanderthal man (na ahn' der tahl). A man-Uke being whose remains have been 

 found in various places in Europe. 



Necator (ne ka' ter). The genus of roundworms to which the hookworm belongs. 



Nectocalyx (neh' to ka' liks) (pL, nectocalyces, nek' to ka' li seez) . One of the swim- 

 ming members of a siphonophore colony. 



Necturus (nek tu' rus). A genus of salamanders; the mud-puppies. 



Nemathelminthes [nem' a thel min' theez) . The phylum of roundworms and their 

 allies. For definition see Chapter XII. 



Nematocyst {nem' a to sist). One of the stinging bodies of Hydra and other ccelen- 

 terates. 



Nematode {nem' a tode). ksxy roundworm of the class Nematoda, phylum Nemathel- 

 minthes. 



Nematomorpha (nem' a to mor' fa) . A group of worm-like animals of uncertain 

 affinities. They have usually been doubtfully included in the Nemathelminthes. 

 For definition see Chapter XII. 



Nemertean (ne mer' te an). Pertaining to the Nemertinea. 



Nemertinea {nem' er tin' e a). A group of worm-like animals of uncertain relation- 

 ships. They are regarded by some as a class of Platyhelminthes. For definition 

 see Chapter XII. 



Nephridium {ne frid' i um) . An excretory organ of certain invertebrate animals 

 (worms, mollusks, etc.), approximately corresponding in function to the kidney 

 of vertebrates. It is commonly a coiled tube, as in the earthworm. 



Nephrostome {nef ro stoma). The opening at the inner end of a nephridium as in 

 the earthworm. Also an opening (originally like that in the earthworm) con- 

 necting the coelom with the blood vessels of the kidney in certain Amphibia. 



Nereis {ne' re is). A genus of marine worms, phylum Annelida. 



Neritina {ner' i ti' na). A genus of snails. 



Nerve (nerv). A bundle of axons or dendrites of nerve cells or of both axons and 

 dendrites. 



Nervous tissue {ner' vus lish' u). Tissue capable of transmitting impulses; as the 



tissues of the brain, spinal cord and nerves. 

 Net-knot {net' not). A thickened portion of the chromatin of a cell nucleus. 



Neural arch {nu' ral arch'). That part of a vertebra above the centrum and neural 

 canal. 



Neural canal {nu' ral ka naV). The opening in a vertebra through which the spinal 

 cord extends. 



Neural crest {nu' ral krest'). One of a number of groups of cells at the sides of the 

 brain and spinal cord of an embryo, from which ganglia and nerves are developed. 



Neural fold (nu' ral fold'). One of the ridges of ectoderm forming the earliest develop- 

 ment of the nervous system. 



Neural groove {nu' ral groov') . An elongated depression between the neural folds of an 

 embryo. 



Neural spine (nu' ral spine'). A projection rising from the middle of the neural arch 

 of a vertebra. 



Neural tube {nu' ral tube'). The tube formed beneath the ectoderm by the union 

 of the neural folds along their crests. 



